The rotator cuff of the shoulder is a group of four muscles that are primarily responsible for internal and external rotation of the arm and shoulder. This muscle group is very prone to injury from overhead throwing, lifting and various activities performed overhead. The lack of flexibility of the rotator cuff is a primary cause of many of these injuries. Stretching these tissues correctly is the way to prevent and or rehabilitate injuries and increase range of motion of these joints, and their associated connective tissues.
The optimal way to stretch a muscle is to do so without causing contraction of the stretched muscle. This can only be accomplished by performing passive static stretching. This method allows stretching force to be applied to the connective tissue of the muscle without causing active bonding of the contractile components. Longtime use of this method of stretching breaks down scar tissue and adhesions and stimulates the healing process of the connective tissue. This results in elongation of the connective tissue fibers which are also less rigid and more elastic. Carefully controlling the amount of tension applied to these tissues during stretching is the safest method. This makes the tissue less likely to reach its end point of flexibility during the stretch-contraction cycle and consequently less prone to tearing and injury.
The rotator is not easily stretched correctly with the arm abducted around 90 degrees, which is the position employed by previously-existing exercisers. Abduction of a shoulder with impingement syndrome causes the supraspinatus muscle of the rotator cuff to contract. When this occurs during stretching it is less effective as a stretch and could possibly irritate or further injure the muscle. One way to stretch the rotator cuff and shoulder into external or internal rotation while putting less stress on the cuff is to move the arm into horizontal adduction. Another way to reduce impingement and stress on the shoulder during internal and external rotation, is to decrease the amount of abduction the arm is placed in while stretching.
Stretching the arm when it is abducted at 90 degrees and internally or externally rotated also puts a stretch on the tissues of the elbow. Having a device that would allow the arm to be extended while in these positions would allow the user to maintain the stretch on the shoulder while changing the forces on the elbow to that which would be pain free and beneficial. When the shoulder is stretched with the elbow bent at 90 degrees, pain may be caused at the elbow which prevents the appropriate level of stretch on the shoulder. Extending the elbow (straight) allows the shoulder to be stretched in this circumstance because the elbow pain will be eliminated. Also, for persons with elbow tendonitis (i.e., tennis elbow, little league elbow), stretching the elbow into proration and supination with the elbow extended (straight at 180 degrees) is beneficial in treating elbow tendonitis.
A currently-used method for stretching the rotator cuff into internal and external rotation while the arm is abducted is to lie on one's back on the edge of a table and let the forearm hang over the edge, while holding a weight in ones' hand. While this stretches the muscles, the weight applies a force against the muscles, which may or may not be the exact level of tension needed to produce a beneficial stretch. This stretch applied to a contracting muscle would be more likely to cause injury, and provide a less effective stretch on the connective tissue. The foregoing method is much more easily applied to the movement of external rotation than internal rotation. Internal rotation done using the above method allows much more movement of the scapula. This would make the likelihood of active contraction during the internal rotation stretching process greater. Another similar method is to have another person hold the arm abducted while moving the forearm into internal and external rotation.
Another method used to stretch the rotator cuff requires the assistance of another person. A partner places the arm in the 90.degree. abducted position, while the user to be stretched lies on the user's back, or is standing. This method has two drawbacks. The first is that a second person is required and the second is that the person applying this force must be very responsive to feedback from the user about the intensity of the stretch. Too much pressure can very easily injure the rotator cuff. Therefore, the user being stretched does not have complete control over the force of the stretch being applied. In other words, the user is required to place his or her injured and sore arm, as well as his or her complete trust, in a therapist's hands. This is particularly a difficult situation, especially in the beginning of a therapy program. Patients tend to guard their muscles during the stretching, resulting in non-voluntary contractions of the muscles being stretched. This can be very painful for the user and frustrating for the therapist. Oftentimes, extended periods are required to do a few short stretches.
Currently, there are devices that are used to increase range of motion of the shoulder known as constant passive motion machines (CPM). These are motorized devices that attach to a chair and are used by physicians after shoulder surgery and manipulations of frozen shoulders. Certain CPM devices can initiate shoulder flexion and abduction as well as combining abduction with external rotation. However, these devices do not allow the user to move into selective levels of horizontal adduction or extend the elbow. These devices also use motors to provide movement and not direct application and control by physical means the user.
There are also a number of machines that strengthen the shoulder and rotator cuff with the arm at 90 degrees of abduction and the elbow flexed at 90 degrees. However, those machines apply resistance via weight plates against gravity. This does not allow the user to control the amount of stretch or tension being applied to the musculature. It is determined by the amount of weight that has been previously loaded onto the machine. This could be more or less than the amount that is beneficial which amount is best measured only by the user during use. A machine that is designed to provide the exact amount of tension in positions that are comfortable and physiologically safe under the current level of injury to the shoulder would provide a better method of prevention and rehabilitation of shoulder and elbow injuries.
It is therefore the object of the present invention to provide a machine for increasing flexibility that can place the user in various levels of abduction, horizontal adduction, internal and external rotation and elbow flexion or extension at the same time. It is a further object that the machine simultaneously stretch the rotator cuff, shoulder and elbow in selective positions. It is another object that the machine provide the user with complete control of the intensity of stretch via self-imposed manual means that places the shoulder and elbow in positions that allow the stretch to be done when other positions would be painfull and therefore not performable. It is yet another object that the machine be adapted to rehabilitate elbow tendonitis by applying proration and supination (internal and external rotation of the forearm) at the proper intensity. It is a final object that the machine be usable to treat elbow problems as well as shoulder problems, or allow treatment of one area when pain in the other prevents certain therapeutic stretching.